I don't know if this would help you, but I've just uploaded the Single Player Framework I've been working on
here. (14MB)
It comes ready-made with all the SP code so that you can just start mapping for it, and the source is included if you want to modify the code. It's got a bunch of new actors to give the mapper as much to work with as possible, and I ported a ton of the Unreal monsters across (all different kinds of Skaarj, Mercs, Slith, etc). It also features a save/load game menu, checkpoint system and transition system (transfers weapons and items over to the next map in the "series" like in Unreal).
I put up a list of the most common new actors
here.